The sun is the source of enormous energy. The solar energy received by the total land of India is about 19 trillion kwh per day, which is about 2.2 million tonnes of oil equivalent. Solar radiation is currently being used to generate electricity via two technologies.
(i) Solar Thermal and (ii) Photovoltaic
The photovoltaic’ system generates electricity directly by solar cells while in soar thermal, the solar radiation is converted to thermal energy at a high temperature which can be used directly or sent through a turbine to generate electricity. In both of the technologies, the solar radiant energy is first converted into thermal or heat energy with the help of solar collectors (pans).
(i) Solar Thermal:
Solar cookers, solar water heaters coupled with geysers and solar air heating systems are some attractive options of utilisation of solar energy for domestic purposes. Solar dryers, solar desalination systems and wood seasoning kilns are now being manufactured by several private manufacturers. .Solar steam generating systems, solar cold storage and solar power generating systems have also been installed and tried successfully. In solar thermal energy, sun’s radiant energy is first focused on solar collectors to generate thermal or heat energy which is later converted to electricity. The use of solar cooker is common now-a-days. OREDA (Orissa Renewable Energy Development Agency) is trying to make it popular in Orissa.
(ii) Solar Photovoltaic:
The process of conversion of sun light directly to electricity is known as photo-electricity or photovoltaic conversion. The devices used are photovoltaic cells or simply solar cells.
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The solar cells are semiconductors and are made from silicon. The cells are made of two chips of silicon crystals with junctions between them. When sunlight falls on the sand witch, it boils the electrons in the silicon crystal and the electron moves through the junction and an electric current is produced. The current is a direct current (d.c.).
Hence it is converted to alternating current (a.c.) before use. The efficiency of the solar energy conversion in photovoltaic is very low, i.e. hardly 12% to 14% and the cost of the silicon based chips are very high. These two reasons are the main hindrance in making it commercially popular.
Solar power, which has the brightest future, is the least popular of the three main non-conventional energy sources (other two are bioenergy and wind), because of the high capital costs and relatively low currents released.”- says Dr. Ved Mitra, Director of the Solar Energy Centre (SEC) the Ministry of Non-convemtional Energy Sources (MNES) at Gwalpahari, on the Delhi-Haryana border. The cost is more than three times than that of power generated by conventional means. Unless there is tremendous technical advance, solar power will remain peripheral to the larger energy scene.
Uses of Solar Energy:
The solar cells are used by satellites to get energy; photovoltaic modules are used for street lighting, pumping water from both shallow and deep wells, to run refrigerators at remote rural areas which store the vaccines kept at primary health centres and very low power T.V. transmitters. Solar lanterns are available for giving light in rural areas.
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But its biggest use in India is found in rural radio telephones of the Department of Telecommunication (DOT). It is the DOT’s annual demand of about 60,000 modules of 70 watt each. Hence several private companies are trying to enter into this field.